1 //===--- AvoidConstParamsInDecls.cpp - clang-tidy--------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8
9 #include "AvoidConstParamsInDecls.h"
10 #include "../utils/LexerUtils.h"
11 #include "clang/ASTMatchers/ASTMatchFinder.h"
12 #include "clang/ASTMatchers/ASTMatchers.h"
13 #include "clang/Lex/Lexer.h"
14
15 using namespace clang::ast_matchers;
16
17 namespace clang::tidy::readability {
18 namespace {
19
getTypeRange(const ParmVarDecl & Param)20 SourceRange getTypeRange(const ParmVarDecl &Param) {
21 return {Param.getBeginLoc(), Param.getLocation().getLocWithOffset(-1)};
22 }
23
24 // Finds the location of the qualifying `const` token in the `ParmValDecl`'s
25 // return type. Returns `std::nullopt` when the parm type is not
26 // `const`-qualified like when the type is an alias or a macro.
27 static std::optional<Token>
findConstToRemove(const ParmVarDecl & Param,const MatchFinder::MatchResult & Result)28 findConstToRemove(const ParmVarDecl &Param,
29 const MatchFinder::MatchResult &Result) {
30
31 CharSourceRange FileRange = Lexer::makeFileCharRange(
32 CharSourceRange::getTokenRange(getTypeRange(Param)),
33 *Result.SourceManager, Result.Context->getLangOpts());
34
35 if (FileRange.isInvalid())
36 return std::nullopt;
37
38 return tidy::utils::lexer::getQualifyingToken(
39 tok::kw_const, FileRange, *Result.Context, *Result.SourceManager);
40 }
41
42 } // namespace
43
storeOptions(ClangTidyOptions::OptionMap & Opts)44 void AvoidConstParamsInDecls::storeOptions(ClangTidyOptions::OptionMap &Opts) {
45 Options.store(Opts, "IgnoreMacros", IgnoreMacros);
46 }
47
registerMatchers(MatchFinder * Finder)48 void AvoidConstParamsInDecls::registerMatchers(MatchFinder *Finder) {
49 const auto ConstParamDecl =
50 parmVarDecl(hasType(qualType(isConstQualified()))).bind("param");
51 Finder->addMatcher(functionDecl(unless(isDefinition()),
52 has(typeLoc(forEach(ConstParamDecl))))
53 .bind("func"),
54 this);
55 }
56
check(const MatchFinder::MatchResult & Result)57 void AvoidConstParamsInDecls::check(const MatchFinder::MatchResult &Result) {
58 const auto *Func = Result.Nodes.getNodeAs<FunctionDecl>("func");
59 const auto *Param = Result.Nodes.getNodeAs<ParmVarDecl>("param");
60
61 if (!Param->getType().isLocalConstQualified())
62 return;
63
64 if (IgnoreMacros &&
65 (Param->getBeginLoc().isMacroID() || Param->getEndLoc().isMacroID())) {
66 // Suppress the check if macros are involved.
67 return;
68 }
69
70 const auto Tok = findConstToRemove(*Param, Result);
71 const auto ConstLocation = Tok ? Tok->getLocation() : Param->getBeginLoc();
72
73 auto Diag = diag(ConstLocation,
74 "parameter %0 is const-qualified in the function "
75 "declaration; const-qualification of parameters only has an "
76 "effect in function definitions");
77 if (Param->getName().empty()) {
78 for (unsigned int I = 0; I < Func->getNumParams(); ++I) {
79 if (Param == Func->getParamDecl(I)) {
80 Diag << (I + 1);
81 break;
82 }
83 }
84 } else {
85 Diag << Param;
86 }
87
88 if (Param->getBeginLoc().isMacroID() != Param->getEndLoc().isMacroID()) {
89 // Do not offer a suggestion if the part of the variable declaration comes
90 // from a macro.
91 return;
92 }
93 if (!Tok)
94 return;
95
96 Diag << FixItHint::CreateRemoval(
97 CharSourceRange::getTokenRange(Tok->getLocation(), Tok->getLocation()));
98 }
99
100 } // namespace clang::tidy::readability
101